Oxidized metallocene-polyolefin waxes

ABSTRACT

Oxidized waxes are obtainable by oxidation of polyolefins obtainable by means of metallocene catalysis and having a molecular weight Mw in the range from 1000 to 40,000 g/mol.

The present invention relates to oxidized waxes obtainable by oxidationof polyolefins obtainable by means of metallocene catalysis and having amolecular weight Mw in the range from 1000 to 40,000 g/mol. Thepolyolefins obtainable by means of metallocene catalysis are, in theinterest of simplicity, hereinafter referred to as metallocenepolyolefins.

In addition, the present invention relates to a process for preparingoxidized polyolefin waxes by oxidation of polyolefins having a molecularweight M_(w) in the range from 1000 to 40,000 g/mol usingoxygen-containing agents at from 140 to 350° C., and also to the use ofoxidized waxes as or in coating compositions, as or in floor polishesand to the use of oxidized polyolefin waxes as or in coatingcompositions for citrus fruits.

Oxidized polyolefin waxes are already known. They are generally obtainedby oxidation of, in general low molecular weight, Ziegler polyethylene,Phillips polyethylene (HDPE) or high-pressure polyethylene (LDPE) usingair or pure oxygen, Kunststoff-Handbuch, volume 4, p. 161 ff.Carl-Hanser-Verlag, 1969.

Such oxidized waxes are already used as coating compositions for variousapplications, for example in the surface treatment of floors or citrusfruits.

The polyolefin wax oxidation forms, inter alia, carboxyl groups in or onthe polymer chains of the starting polyolefin, the number of which canbe determined by means of the acid number. A high acid number of thewaxes is generally advantageous since the waxes can be dispersed andapplied better.

In the oxidation of known Phillips polyethylene waxes, Zieglerpolyethylene waxes or, in particular, high-pressure polyethylene waxes,a great reduction in the melting point of the oxidized waxes compared tothe starting polymer is observed and this is associated with anundesired reduction in the hardness of the oxidized waxes. However, ahigh hardness and thus a high melting point of the oxidized waxes isadvantageous for use as or in coating compositions, for example in floorpolishes or for preserving citrus fruits.

Furthermore, the oxidation of the known polyolefin waxes results in anunfavorable ratio of acid number to saponification number of <1:1 andthis generally has an adverse effect on the dispersibility of the waxesin aqueous media. The dispersibility can generally be improved byincreasing acid number and saponification number.

It is an object of the present invention to find a remedy to thedisadvantages mentioned and to provide, in particular, oxidizedpolyolefin waxes having a relatively high molecular weight and at thesame time a high acid number, high saponification number andcomparatively high hardness, and also a high melting point. Furthermore,it is an objective of the present invention to provide an oxidationprocess for polyolefins which makes it possible to obtain oxidizedpolyolefin waxes having the abovementioned desired properties.

We have found that these objects are achieved by oxidized waxesobtainable by oxidation of polyolefins obtainable by means ofmetallocene catalysis and having a molecular weight M_(w) in the rangefrom 1000 to 40,000 g/mol and a process for preparing oxidizedpolyolefin waxes by oxidation of polyolefins having a molecular weightMw in the range from 1000 to 40,000 g/mol using oxygen-containing agentsat from 140 to 350° C., wherein the polyolefins used are ones which areobtainable by means of metallocene catalysis.

The present invention also provides for the use of oxidized waxes as orin coating compositions, the use of oxidized waxes as or in floorpolishes and the use of oxidized waxes as or in coating compositions forcitrus fruits.

The polyolefins on which the oxidized waxes are based have a weightaverage molecular weight M_(w), determined by gel permeationchromatography (GPC) in 1,2,4-trichlorobenzene at 135° C. using apolyethylene or polypropylene standard, in the range from 1000 to 40,000g/mol, preferably in the range from 2000 to 20,000 g/mol. Thepolydispersity M_(w)/M_(n) of the polyolefins on which the oxidizedwaxes are based, measured by GPC as described, is generally in the rangefrom 1.5 to 3.0, preferably in the range from 1.8 to 2.5.

The polyolefins on which the oxidized waxes are based can be obtained bypolymerization of the corresponding monomers in the presence ofmetallocene catalysts (metallocene catalysis).

Well suited monomers are ethylene and C₃-C₁₀-alk-1-enes, i.e. propylene,1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene.Preference is given to using ethylene and/or propylene as monomers.

The monomers can be homopolymerized or copolymerized with one another inany ratio. Preferred polyolefins on which the oxidized waxes are basedare ethylene homopolymers having a density in the range from 0.90 to0.98 g/cm³, preferably in the range from 0.94 to 0.97 g/cm³, and anM_(w), determined by GPC as described above, in the range from 1000 to40,000 g/mol, preferably in the range from 2000 to 20,000 g/mol.

Other suitable starting polyolefins are ethylene-C₃-C₁₀-alk-l-enecopolymers containing a total of from 0.1 to 15 mol %, preferably from 1to 10 mol %, mol %, based on the copolymer, of structural units derivedfrom the alk-1-ene or alk-1-enes. Preferred ethylene-alk-1-enecopolymers are ethylene-propylene copolymers containing from 0.1 to 10mol %, preferably from 1 to 5 mol %, based on the copolymer, ofstructural units derived from the propylene. The copolymers generallyhave an M_(w), determined by GPC as described above, in the range from1000 to 40,000 g/mol, preferably in the range from 2000 to 20,000 g/mol.

Further preferred polyolefins on which the oxidized waxes are based areisotactic propylene homopolymers having an isotactic pentad mnmnmmcontent, determined by ¹³C-NMR spectroscopy, in the range from 90 to 98%and an Mw, determined by GPC as described above, in the range from 1000to 40,000 g/mol, preferably in the range from 2000 to 20,000 g/mol.

Other suitable base polyolefins are copolymers of propylene withethylene and/or C₄-C₁₀-alk-1-enes. These propylene copolymers usuallycontain a total of from 0.1 to 15 mol %, preferably from 1 to 10 mol %,based on the copolymer, of structural units derived from the ethyleneand/or the C₄-C₁₀-alk-1-enes. Preferred propylene copolymers arepropylene-ethylene copolymers containing from 0.1 to 10 mol %,preferably from 1 to 5 mol %, based on the copolymer, of structuralunits derived from the ethylene. The propylene copolymers generally havean M_(w), determined by GPC as described above, in the range from 1000to 40,000 g/mol, preferably in the range from 2000 to 20,000 g/mol.

The monomers are homopolymerized or copolymerized in the presence ofmetallocene catalysts (metallocene catalysis).

For the purposes of the present invention, metallocene catalysts aresubstances which are generally formed by combining a transition metalcompound or a plurality of transition metal compounds, preferably oftitanium, zirconium or hafnium, which contain at least one ligand whichis in the widest sense a derivative of cyclopentadienyl ligands with anactivator, also known as cocatalyst or compound capable of formingmetallocenium ions, and are generally polymerization-active toward themonomers described. Such catalysts are described, for example, in EP-A 0545 303, EP-A 0 576 970 and EP-A 0 582 194. The catalyst systemsaccording to the present invention generally comprise as activeconstituents

A) a metallocene complex or a plurality of metallocene complexes of theformula (I)

 where the substituents and indices have the following meanings:

M is titanium, zirconium, hafnium, vanadium, niobium, tantalum,chromium, molybdenum or tungsten,

X¹, X² are fluorine, chlorine, bromine, iodine, hydrogen, C₁-C₁₀-alkyl,C₆-C₁₅-aryl, —OR⁶ or —NR⁶R⁷,

 where R⁶, R⁷ are C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl, arylalkyl,fluoroalkyl or fluoroaryl each having from 1 to 10 carbon atoms in thealkyl radical and from 6 to 20 carbon atoms in the aryl radical,

R¹ to R⁵ are hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl whichmay in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl orarylalkyl, or two adjacent radicals may together form a cyclic grouphaving from 4 to 15 carbon atoms, or Si(R⁸)₃, where

R⁸ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

Z is X¹, X² or

where the radicals

R⁹ to R¹³ are hydrogen, C₁-C₂₀-alkyl, 5- to 7-membered cycloalkyl whichmay in turn bear a C₁-C₁₀-alkyl group as substituent, C₆-C₁₅-aryl orarylalkyl, or two adjacent radicals may together form a cyclic grouphaving from 4 to 15 carbon atoms, or Si(R¹⁴)₃ where

R¹⁴ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl or C₃-C₁₀-cycloalkyl,

 or the radicals

R⁴ and Z together form a —[Y(R¹⁵)(R¹⁶)]_(n)—E— group in which

Y can be identical or different and are each silicon, germanium, tin orcarbon,

R¹⁵, R¹⁶ are hydrogen, C₁-C₁₀-alkyl, C₃-C₁₀-cycloalkyl or C₆-C₁₅-aryl,

n is 1, 2, 3 or 4,

E is

 or A, where A is —O—, —S—,

 where R¹⁷ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl, alkylaryl orSi(R¹⁸)₃

 where R¹⁸ is C₁-C₁₀-alkyl, C₆-C₁₅-aryl, C₃-C₁₀-cycloalkyl or alkylaryland

B) is a compound capable of forming metallocenium ions.

Well suited transition metal compounds (I) are

where Z is X¹, X² or

where R⁴ and Z do not form a

^(—)[Y (R¹⁵) (R¹⁶)]_(n) ^(—)E^(—) group.

Thus, the term metallocene complex or metallocene does not only refer tothe bis(η-cyclopentadienyl)metal complexes and their derivatives.

The radicals X¹, X² can be identical or different; they are preferablyidentical.

Particularly useful compounds of the formula (Ia) are those in which

R¹ and R⁹ are identical and are hydrogen or a C₁-C₁₀-alkyl group,

R⁵ and R¹³ are identical and are hydrogen, methyl, ethyl, isopropyl ortert-butyl,

R², R³, R¹⁰ and R¹¹ have the meanings R³ and R¹¹ are C₁-C₄-alkyl, R² andR¹⁰ are hydrogen or two adjacent radicals R² and R³ or R¹⁰ and R¹¹together form a cyclic group having from 4 to 12 carbon atoms,

R¹⁵, R¹⁶ are C₁-C₈-alkyl,

M is titanium, zirconium or hafnium,

Y is silicon, germanium, tin or carbon and

X¹, X² are chlorine or C₁-C₄-alkyl.

Examples of particularly useful complexes are, inter alia:

dimethylsilanediylbis(cyclopentadienyl)zirconium dichloride,

dimethylsilanediylbis(indenyl)zirconium dichloride,

dimethylsilanediylbis(tetrahydroindenyl)zirconium dichloride,

ethylenebis(cyclopentadienyl)zirconium dichloride,

ethylenebis(indenyl)zirconium dichloride,

ethylenebis(tetrahydroindenyl)zirconium dichloride,

tetramethylethylene-9-fluorenylcyclopentadienylzirconium dichloride,

dimethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)-zirconiumdichloride,

dimethylsilanediylbis(3-tert-butyl-5-ethylcyclopentadienyl)-zirconiumdichloride,

dimethylsilanediylbis(3-tert-butyl-5-methylcyclopentadienyl)-dimethylzirconium,

dimethylsilanediylbis(2-methylindenyl)zirconium dichloride,

dimethylsilanediylbis(2-isopropylindenyl)zirconium dichloride,

dimethylsilanediylbis(2-tert-butylindenyl)zirconium dichloride,

diethylsilanediylbis(2-methylindenyl)zirconium dibromide,dimethylsilanediylbis(3-methyl-5-methylcyclopentadienyl)-zirconiumdichloride,

dimethylsilanediylbis(3-ethyl-5-isopropylcyclopentadienyl)-5 zirconiumdichloride,

dimethylsilanediylbis(2-methylindenyl)dimethylzirconium,dimethylsilanediylbis[3,3, ′-(2-methylbenzindenyl)]zirconium dichloride,

dimethylsilanediylbis(2-methylindenyl)hafnium dichloride,

dimethylsilanediylbis[3,3′-(2-methylbenzindenyl)]hafnium dichloride,

dimethylsilanediylbis[3,3, -(2-methylbenzindenyl)]dimethyl-zirconium.

Particularly useful compounds of the formula (Ib) are those in which

M is titanium or zirconium,

X¹, X² is chlorine or C₁-C₁₀-alkyl,

Y is silicon or carbon when n=1 or is carbon when n=2,

R¹⁵, R¹⁶ is C₁-C₈-alkyl, C₅- or C₆-cycloalkyl or C₆-C₁₀-aryl,

A is —O—, —S—,

 and

R¹ to R³ and R⁵ are hydrogen, C₁-C₁₀-alkyl, C₃-C₁₀-cycloalkyl,C₆-C₁₅-aryl or Si(R⁸)₃, or two adjacent radicals form a cyclic grouphaving from 4 to 12 carbon atoms.

Particularly useful compounds of the formula (Ic) are those in which Zis X¹ or X² and X¹ and X² are identical. Preferably, X¹, X² are thenhalogen or C₁-C₄-alkyl and R¹ to R⁵ in (Ic) are then C₁-C₄-alkyl.

When Z in (Ic) is

X¹, X² are preferably halogen or C₁-C₄-alkyl and R¹ to R⁵ and R⁹ to R¹³are preferably hydrogen, C₁-C₂₀-alkyl, such as methyl, ethyl, n-propyl,tert-butyl, n-hexyl, n-octyl, in particular octadecyl.

Examples of particularly useful compounds (Ic) are pentamethyl-cyclopentadienyltrimethyltitanium, pentamethylcyclopentadienyl- titaniumtrichloride and bis(octadecylcyclopentadienyl)zirconium dichloride,biscyclopentadienylzirconium dichloride, bis(penta-methylcyclopentadienyl)zirconium dichloride, bis(methylcyclo-pentadienyl)zirconium dichloride, bis(n-butylcyclopentadienyl)-zirconium dichloride, bis(n-octadecylcyclopentadienyl)zirconiumdichloride.

Such transition metal compounds (I) can be synthesized by methods knownper se, preferably by reacting the appropriately substitutedcycloalkenyl anions with halides of the transition metals, for exampletitanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium,molybdenum or tungsten. Examples of appropriate preparative methods aredescribed, inter alia, in Journal of Organometallic Chemistry, volume369 (1989), pages 359 to 370.

Compounds B) capable of forming metallocenium ions are known to thoseskilled in the art and are described, for example, in WO 95/14044.

Well suited compounds B) are, for example, open-chain or cyclicaluminoxane compounds of the formula (II) or (III)

where R¹⁹ is a C₁-C₄-alkyl group, preferably a methyl or ethyl group,and m is an integer from 5 to 30, preferably from 10 to 25.

The preparation of these oligomeric aluminoxane compounds is usuallycarried out by reacting a solution of trialkylaluminum with water and isdescribed, inter alia, in EP-A 284 708 and U.S. Pat. No. 4,794,096.

The oligomeric aluminoxane compounds obtained in this way are generallyin the form of mixtures of both linear and cyclic chain molecules ofdifferent lengths, so that m is to be regarded as a mean value. Thealuminoxane compounds can also be present in admixture with other metalalkyls, preferably aluminum alkyls.

It has been found to be advantageous to use the metallocene complexesand the oligomeric aluminoxane compound in such amounts that the atomicratio of aluminum from the oligomeric aluminoxane compound to thetransition metal from the metallocene complexes is in the range from 1:1to 10⁵:1, in particular in the range from 100:1 to 1000:1.

As compounds B) capable of forming metallocenium ions, it is alsopossible to use coordination compounds selected from the groupconsisting of strong, uncharged Lewis acids.

Preferred strong, uncharged Lewis acids are compounds of the formula IV

M²X³X⁴X⁵  (IV),

where

M² is an element of main group III of the Periodic Table, in particularB, Al or Ga, preferably B,

X³, X⁴ and X⁵ are hydrogen, C₁-C₁₀-alkyl, C₆-C₁₅-aryl, alkylaryl,arylalkyl, haloalkyl or haloaryl each having from 1 to 10 carbon atomsin the alkyl radical and from 6 to 20 carbon atoms in the aryl radicalor fluorine, chlorine, bromine or iodine, in particular haloaryls suchas fluoroaryls, preferably pentafluorophenyl.

Particular preference is given to compounds of the formula (IV) in whichX³, X⁴ and X⁵ are identical, preferably tris(pentafluoro-phenyl)borane.These compounds and methods of preparing them are known per se and aredescribed, for example, in WO 93/3067.

It has been found to be particularly useful for the molar ratio of boronfrom the compound capable of forming metallocenium ions to transitionmetal from the metallocene complex to be in the range from 0.1:1 to10:1, in particular in the range from 1:1 to 5:1.

The compounds B) capable of forming metallocenium ions are usually usedalone, in admixture with one another or in admixture with organometalliccompounds of the first to third main groups of the Periodic Table of theElements, for example n-butyllithium, di-n-butylmagnesium,butyloctylmagnesium, trimethylaluminum, triethylaluminum,triisobutylaluminum, diisobutylaluminum hydride; the mixing ratio of thecomponents is generally not critical.

Preference is given to using C₁-C₁₀-alkylaluminoxanes, in particularmethylaluminoxanes, as compound B) capable of forming metalloceniumions.

The preparation of the polymers from the olefinically unsaturatedhydrocarbons can be carried out in the customary reactors, eithercontinuously or preferably batchwise.

Suitable reactors are, inter alia, continuously operated stirredvessels; if desired, a cascade comprising a plurality of stirred vesselsconnected in series can also be used. The polymerization reactions canbe carried out in the gas phase, in suspension, in liquid orsupercriticial monomers or in inert solvents.

The polymerization conditions are not critical per se. Pressures of from0.1 to 500,000 kPa, preferably from 100 to 250,000 kPa p and inparticular from 100 to 100,000 kPa, and temperatures of from 0 to 450°C., preferably from 20 to 250° C. and in particular from 50 to 100° C.,have been found to be suitable.

The mean molecular weight of the polymers can be controlled by themethods customary in polymerization technology, for example by feedingin molecular weight regulators, e.g. hydrogen, which generally lead to areduction in the molecular weight of the polymer or by varying thepolymerization temperature, in which case high polymerizationtemperatures usually lead to reduced molecular weights.

Suitable processes for preparing polyolefin waxes by means ofmetallocene catalysis are described in WO 88/02009 (high-pressureprocess) and in EP-A 0 321 851, EP-A 0 416 566 and EP-A 0 571 882.

In a preferred process, polyethylene waxes in particular are prepared bypolymerization of ethylene under high-pressure conditions. For thispurpose, the ethylene and any further C₃-C₁₀-alk-1-enes desired arecompressed to pressures above 50,000 kPa, preferably from 100,000 to350,000 kPa. To initiate the polymerization, a catalyst solutioncomprising a suitable activator (for example aluminum alkyl and/ormethylaluminoxane) or a borate (e.g. N,N-dimethylaniliniumtetrakis(pentafluoro- phenyl)borate, is then added. The reactiontemperature generally rises to values up to 300° C., preferably to from200 to 250° C. The form of the reactor is not critical per se;conceivable configurations are a continuously operated tube reactor or acontinuously operated stirring autoclave. To prepare the polyolefinoxidates of the present invention, a particularly suitable catalystsystem is bis(n-butylcyclopentadenyl)zirconium dichloride activated withN,N-dimethylanilinium tetrakis(penta- fluorophenyl)borate.

The oxidation of the polyolefins on which the oxidized waxes are basedcan be carried out using oxygen, oxygen-containing gases, preferablyair. Preference is given to using air for oxidizing the polyolefins. Toaid the oxidation, it is possible to add organic peroxides such asdi-tert-butyl peroxide; the addition of heavy metal salts such asmanganese acetate is also conceivable.

Suitable oxidation processes for polyolefin waxes are known from, forexample, DE-A-2035706.

In a preferred process, the metallocene polyolefin according to thepresent invention, preferably an ethylene homopolymer, is reacted withoxygen-containing gases, preferably air, in a tube reactor or a stirringautoclave at from 140 to 350° C., preferably from 150 to 250° C., and apressure in the range from 100 to 20,000 kPa, preferably in the rangefrom 500 to 4000 kPa. The amount of oxygen fed in is then generally inthe range from 0.1 to 1000 l of oxygen/hxkg of wax, preferably in therange from 1 to 50 l of oxgyen/hxkg of wax.

The oxidized polyolefin waxes obtainable in this way, in particular theoxidized waxes from ethylene homopolymer, have a ratio of acid number tosaponification number in the range from 1:1 to 1:4, preferably in therange from 1:1 to 1:2.

The acid number was determined by titration in accordance with DIN53402. The saponification number was determined by titration inaccordance with DIN 53401. Suitable acid numbers are 1-150 mg KOH/g,preferably 10-50 mg KOH/g and particularly preferably 15-30 mg KOH/g.The melting point of the oxidized waxes of the present invention,determined by Differential Scanning Calorimetry (DSC), in accordancewith DIN 51007, is usually in a range from 90 to 125° C., preferablyfrom 110 to 125  C.

The hardness of the oxidized waxes of the present invention determinedusing the ball indentation test, in accordance with DIN 50133, isusually in a range from 800 to 2000 N/mm², preferably from 1000 to 1500N/mm².

The viscosity of the oxidized waxes of the present invention, measuredusing the Ubbelohde melt visocisty method as 140° C. in accordance withDIN 51562, is usually in the range from 100 to 10,000 cst, preferablyfrom 200 to 5000 cst.

The waxes of the present invention are useful as coating compositions oras a component of coating compositions. The coating compositiongenerally has a high hardness and a high gloss.

EXAMPLES

The examples according to the present invention were carried out usinghomopolyethylene waxes which had been prepared by polymerization ofethylene by the high-pressure process. The polymerization was carriedout in a continuously operated 1 l high-pressure autoclave fitted with astirring motor. Ethylene and hydrogen were continuously introduced intothe autoclave under pressure, with the polymerization pressure in theinterior of the autoclave being regulated at 150,000 kPa. In a separatemake-up vessel, the solutions of triisobutyl-aluminum in heptane andN,N,dimethylanilinium tetrakis(pentafluorophenyl)borate in toluene wereadded to a solution of bis(n-butylcyclopentadienyl)zirconium dichloridein a molar ratio of Zr:Al 1:400 and Zr:B 1:1.2. The active catalystsolution was then immediately, without a further residence time, meteredcontinuously into the autoclave and the reaction temperature was held at240° C. The hydrogen addition was 120 l/h. The starting waxes have thefollowing properties:

M.p. 1) Hardness 2) Sample [° C.] [N/mm²] Viscosity [140° C.] 3) [cst.]1 128.3 1170 350 1C*⁾ 128.7 1270 380 *⁾Ziegler polyethylene wax PE 130from Hoechst 1) measured in accordance with DIN 51007 2) measured inaccordance with DIN 50133 3) measured in accordance with DIN 51562

Examples 1, 1C

The oxidations of the waxes 1 and 1c (see table above) were carried outin a stirred (impeller stirrer) 1l steel autoclave with pressuremaintenance device. The wax to be oxidized was placed in the autoclaveand heated to 160° C. After the wax had melted, the stirrer was switchedon and air was passed through (30l/h kg). The reaction was stopped whenthe desired acid number had been reached, the oxidized wax was drainedoff and analyzed.

M.p. Hardness Visc. 140° C. Acid number 1) Starting Example [° C.] [bar][° C.] [mg KOH/g] wax 1 121.5 730 125 20.5 1 1C 117.2 660 150 20.5 1V 1)measured in accordance with DIN 53402

Use examples

20 parts of oxidate wax from Examples 1, 1C were admixed with 2 parts ofmorpholine and 5 parts of olein in 68 parts of water and heated at 150°C. for 15 minutes in a pressure autoclave. The emulsion obtained in thisway was cooled to room temperature, filtered and a sample for measuringthe gloss was subsequently taken. 3 ml of the dispersion were placed ina 60 μm box coater and applied to leather; after application, the glossvalues [85°] were measured (instrument from Dr. Lange, UME-2 instrument)

without coating: 5.8 with dispersion from Example 1 8.6 with dispersionfrom Example 1V 6.4

We claim:
 1. An oxidized wax produced by the process of oxidizing a polyolefin produced by olefin polymerization using metallocene catalysts and having a molecular weight M_(w) in the range from 1000 to 40,000 g/mol, wherein the ratio of acid number to saponification number of the oxidized wax is in the range from 1:1 to 1:4.
 2. An oxidized wax as claimed in claim 1, wherein the polyolefin used is an ethylene homopolymer or copolymer.
 3. A process for preparing an oxidized polyolefin wax by oxidation of a polyolefin having a molecular weight M_(w) in the range from 1000 to 40,000 g/mol using oxygen-containing agents at from 150 to 350° C., wherein the polyolefin used is produced by olefin polymerization using metallocene catalysis.
 4. A process as claimed in claim 3, wherein the oxygen-containing agent used is air.
 5. A process as claimed in claim 3, wherein the polyolefin used is an ethylene homopolymer or copolymer.
 6. A coating composition containing the oxidized wax of claim
 1. 7. A floor polish containing the oxidized wax of claim
 1. 8. A coating composition for citrus fruits containing the oxidized wax of claim
 1. 